A large variety of machines for performing some type of operation on stacks of sheets are well known in the art, and typical amongst these are machines for stitching, stapling or punching holes in a collation of such sheets. These machines are most often utilized in conjunction with collating machines which take individual sheets of printed material from stacks and collate these sheets into a proper sequence, for example, to form a booklet or pamphlet containing a certain number of pages arranged in a desired order. The collating machine and the stitching, stapling or punching machine, as the case may be, are operatively associated together in such a way that the collating machine feeds sheets from successive stacks serially onto a receiving tray of the stitching, stapling, or punching machine, on which the sheets are stacked one on top of the other. The sheets are halted on the receiving tray of the stitching, stapling or punching machine in a generally stacked arrangement, and suitable mechanism in the stitching, stapling or punching machines operates to perform the desired function on the stack of sheets. Before this can take place, however, the sheets must be brought into exact registration with each other so that, when the desired operation has been performed, all edges of the sheets in the stack are uniform with each other.
This requirement is achieved by guiding the incoming sheets into proper registration both laterally and longitudinally with respect to the direction of travel of the sheets. Generally, lateral registration has not presented much of a problem since it is a relatively simple matter, as is well known in the art, to provide adjustable side guides which define a channel through which the sheets are moved by whatever feeding mechanism is provided to feed the sheets onto the receiving tray of the stitching, stapling or punching machine, as the case may be. If the side guides are properly adjusted to define a channel substantially the width of the sheets, with no more clearance between the side guides and the edges of the incoming sheets than is necessary for free movement of the sheets, it is a relatively simple matter to align the sheets laterally because the sheets will follow the channel defined by the side guides during their forward movement from the feeding mechanism onto the receiving tray.
Longitudinal registration of the sheets presents a considerably more serious problem than does lateral registration for the reason that longitudinal registration cannot take place until the sheets have reached a predetermined position on the receiving tray and have been brought to a halt by virtue of some obstructing means located in the path of movement of the sheets and beyond which the sheets cannot move until the desired operation has been performed by the stitching, stapling or punching machine. At this point, the rear edge of the incoming sheets must of necessity have passed the jogging device which operates on the rear edge of the sheets, and the jogging device must now operate on sheets which have effectively come to a rest one on top of another. Because of this, it is necessary that any jogging device have a predetermined special relationship with respect to the obstructing mechanism which halts the forward movement of the incoming sheets, and that this special relationship be substantially commensurate with the length of the sheets being registered. In other words, taking into account the degree of movement of the jogging device, it must be located along the tray approximately the same distance from the obstructing mechanism as the length of the sheets being registered. It is apparent that in order for the jogging device to be operable on sheets of varying length, it must be adjustable along the receiving tray in the direction of movement of the sheets.
Typically in prior art machines, as represented by U.S. Pat. No. 3,076,196, a jogging device has been mounted on suitable frame portions of the machine and has incorporated some means for rendering the jogging device adjustable in the direction of movement of the sheets. The disadvantage has been, however, that the jogging device has had to incorporate its own driving motor and the jogging device with the motor has been made adjustable by means which prevented the operator from making any necessary adjustments in a simple and convenient manner. Usually, the jogging device could only be adjusted with the use of tools for loosening connecting devices to allow the jogging device to be loosened on a mounting, move to a desired position, and retightened in the new position, all of which presented an inconvenience and often times difficult procedure for the machine operator. The extent of movement of the prior art devices was usually quite limited in view of interference with other operating components of the machine on which the jogging device is mounted. Another disadvantage of prior art jogging devices is that they often tend to cause the sheets to bounce back and forth against the obstructing means by virtue of the angle at which the jogging finger strikes the rear edge of the sheets, thereby preventing precise registration of the sheets in the longitudinal direction. This is caused by the jogging finger striking the rear edge of the sheets in a slightly upward direction rather than directly along the plane of the sheets or in a slightly downward direction.